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  • evolution  (52)
  • crystal structure
  • kinetics
  • morphology
  • Springer  (148)
  • 2000-2004
  • 1990-1994  (148)
  • 1994  (148)
Collection
Publisher
Years
  • 2000-2004
  • 1990-1994  (148)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 24 (1994), S. 759-762 
    ISSN: 1572-8854
    Keywords: Sulfonamide ; methanesulfonanilide ; crystal structure ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, crystallizes in the triclinic space group $$P\bar 1$$ witha=8.232(4),b=9.159(2),c=10.230(3)Å. α=74.07(3)°, β=72.50(4)°, γ=63.65(3)° andZ=2. The structure was solved by direct methods and refined by full matrix least squares methods toR=0.054 for 1817 observed reflections. The plane containing the nitrogen and sulfur atoms is perpendicular to the aromatic plane. One of the S−O bonds in each methanesulfonyl group is in nearly eclipsed conformation with the N−C bond.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 24 (1994), S. 437-440 
    ISSN: 1572-8854
    Keywords: Ca(C4H4O4)·H2O ; pentagonal pyramid ; calcium succinate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of calcium succinate monohydrate, Ca(C4H4O4)·H2O, has been determined by single crystal X-ray diffraction. The crystals are monoclinic witha=11.952(2),b=9.691(2),c=11.606(2)Å, β=108.81(1)°, space group C2/c,Z=8,V=1272.49 Å3,d m =1.80, andd c =1.818 Mg m−3. The structure was refined by full-matrix least-squares techniques toR=0.027,R w =0.040, for 829 reflections with1≥3δ(I). Ca is coordinated to seven oxygen atoms, and the coordination polyhedron is best described as a pentagonal bipyramid. One carboxylate group in the succinate ion is bonded to three different Ca ions, forming a four-membered chelate ring with one Ca ion is bonded to three different Ca ions, forming a four-membered chelate ring with one Ca ion and unidentate bridge bonds to two other Ca ions. The other carboxylate group is bonded to two Ca ions through unidentate bonds. The structure is highly polymeric. The general structural features are nearly identical to those of calcium adipate monohydrate.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 4 (1994), S. 289-299 
    ISSN: 1572-8870
    Keywords: Graft copolymers ; polysiloxanes ; macromer ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Poly(4-t-butoxycarbonyloxystyrene)-g-poly(dimethylsiloxane) and poly(t-butylmethacrylate)-g-poly(dimethylsiloxane) with various chemical compositions were synthesized via free radical polymerization of 4-t-butoxycarbonyloxystyrene (TBCS) or t-butylmethacrylate (TBMA) with silicone macromers. These macromers were prepared by anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D3) and subsequent termination with a chlorosilane compound having a methacrylate functionality. The morphology of the graft copolymer systems was investigated by DSC and TEM.
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  • 4
    ISSN: 1572-8862
    Keywords: Tungsten ; isomeric forms ; crystal structure ; triple bonds ; interconversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A thorough study of compounds with the formula W2Cl4(NHCMe3)2(PR3)2, withR 3=Me3, Et3, Prg n 3 Me2,Ph, is reported. In addition to the previously reported crystalline compounds, namely Ia,trans-W2Cl4(NHCMe3)2(PMe3)2 in space group Pmmn;3a,trans-W2Cl4(NHCM3)2(PEt3)2 in space group P21/a (or P21/c); and4,cis-W2Cl4(NHCMe3)2(PMe2Ph)2 in Pna21, we have obtained and structurally characterized the following new substances,1b,trans-W2Cl4,(NHCMe3)2(PMe2)2, space group P21/c,a= 12.233 (4) Å,b= 12.872 (4) Å,c=17.095 (5) Å,β=93.52 (2)°,Z=4,V=2687 (1) Å3 2,cis-W2Cl4(NHCMe3)2(PMe3)2, P21/c,a=9.673 (4) Å,b=17.249 (4) Å,c=16.244 (5) Å,β=99.63 (3),Z = 4 ,V=2669 (1) Å.3b,trans-W2Cl4(NHCMe3)2(PEt3)2, Pl,a=16.850 (3) Å,b=17.797 (3) Å,c= 11.459 (2)Å,α= 101.02 (1),β= 103.13°, y=84.23 (1)°,Z=4,V= 3279 (1) Å5,trans-W2Cl4(NHCM3)2(PMe2Ph)2, Fdd2,a=39.563 (8) Å at 20°C; 39.325 (10) Å at -6O°C,b = 57.543 (17) Å at 20°C; 57.186 (16) Å at -60°C,c= 8.810 (1) Å at 20°C; 8.770 (1) Å at - 60°C ,Z=24,V=20057 (7) Å3 (20°C), 19723 (8) Å3 ( - 60°C) .6,trans-W2Cl4(NHCMe3 2(PPrn 3)2, Pl,a= 17.287 (2) Å (20°C); 17.077 (5) Å (-60°C),b= 19.119 (2) Å (20°C); 18.952 (6) Å (-60°C),c= 12.713 (1) Å (20°C); 12.668 (4) Å (-60°C),Z=4,V= 3980 (1) Å3 (20°C), 3898 (2) ,Å3 ( - 60°C). In addition, the structure of3a was re-determined and refined so that the disorder ratio was a refined parameter, leading to a value of 0.520:0.480 instead of being arbitrarily fixed at 0.50:0.50. In all of the structures the molecules are held in eclipsed (but very distorted) rotational conformations and the W-W distances are all within the range of 2.305-2.330 Å. As will be shown in a later paper, for all phosphines, thecis andtrans isomers are of similar stability and an equilibrium mixture exists in solution. It is also shown that1a and3a do not contain unexpectedly short W-N bonds as previously reported.
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  • 5
    ISSN: 1572-8862
    Keywords: Mixed metal cluster ; alkyne ; diphenylacetylene ; platinum ; osmium ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The new platinum-osmium alkyne cluster complex Pt2Os4(CO)8(μ3-PhC2Ph)3 (μ 4-PhC2Ph),2, was obtained from the reaction of Pt2Os4(CO)18,1b, with PhC2Ph and was characterized by IR.1H NMR and single-crystal X-ray diffraction analyses. The cluster of compound2 consists of an osmium capped Pt2Os3 square pyramid. It aLso contains three triply bridging and one quadruply bridging diphenylacetylene ligands. Crystal data for2: space group PI,a = 12.530(2) Å,b = 21.565(4) Å,c = 11.284(2) Å,α = 100.31(2),β = 111.89(1),β = 76.78(2),Z = 2, 3879 reflections,R = 0.032.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical crystallography 24 (1994), S. 731-737 
    ISSN: 1572-8854
    Keywords: Synthesis ; crystal structure ; IR data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis, crystal structure and IR data are reported for Na2[Zn(CMA)4]·2EtOH·7H2O, where CMA− is the 9,10-dihydro-9-oxo-10-acridinacetate ion. The complex crystallizes in the monoclinic space group P2/n, with cell dimensionsa=17.335(9),b=8.440(5),c=21.875(12) Å, β=91.94(5)°,Z=2. The structure was solved by direct methods and refined to a finalR value of 0.0363 for 3022 non-zero reflections. The Zn2+ ion occupies twofold axis and is coordinated to four carboxylate ligands, the ZnO4 tetrahedron is considerably distorted with Zn−O distances of 1.978(3) and 1.961(3)Å. Each Na+ cation interacts with two water, one ethanol, and three carboxylate O atoms comprising distorted octahedron. The Zn2+ and Na+ cations are linked through monooxygen and syn-syn carboxylate bridges forming a trinuclear, mixed-metal cluster. The Zn...Na separation is 3.267(2)Å and Na...Na distance equals 3.520(2)Å. All oxygen bonded H-atoms are utilized in hydrogen bonds. The acridone rings overlap in the crystal with the 3.5 Å interlayer separations. The compound has been characterized by IR spectroscopy.
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  • 7
    ISSN: 1572-8854
    Keywords: Pyrimidine ; uracil ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new and easy method for the preparation of 1,3,7,9-tetramethylpyrido-[2,3-d∶6,5-d′]-dipyrimidine-2,4,6,8-tetrone is described. The structure of this compound has been solved by means of X-ray diffraction methods. The chemical characterization by spectral (mass, ultraviolet, infrared, and proton nuclear magnetic resonance) and thermal (thermogravimetry and differential scanning calorimetry) method is also reported. The compound is monoclinic, space groupP21/c,a=12.720(5),b=13.688(7),c=8.079(2) Å, β=107.06(4)°,Z=4. The structure consists of discrete tricyclic molecules, stacking playing an important role in crystal packing.
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  • 8
    ISSN: 1572-8854
    Keywords: Centrosymmetric ; symmetry ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the centrosymmetric triclinic space group $$P\bar 1$$ (C 1 l ; No.2) witha=9.9143(10) Å,b=10.2616(11) Å,c=10.7715(10) Å, α=113.887(8)°, β=109.197(8)°, γ=90.699(9)°,V=932.78(17) Å3 andZ=1. A total of 4869 data were collected and merged to a set of 2450 independent reflections; the structure was solved and refined toR=1.42% andwR=1.94%. The molecule lies on a site of $$\bar 1$$ symmetry and is disordered, with obvious scrambling of carbonyl and chloride ligands. Resulting bond lengths include Ir−P=2.339(1) Å, Ir−Cl=2.398(4) Å and Ir−CO=1.808(15) Å.
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  • 9
    ISSN: 1572-8862
    Keywords: Mixed metal ; platinum ; ruthenium ; alkyne ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstarct The ten metal cluster complex Pt2Ru8(CO)23(µ3−H)2, 1 was found to react with EtC2Et to form a new ten metal tris-alkyne complex Pt2Ru8(CO)18(µ3−EtC2Et)2 (µ4−EtC2Et),2 in 35% yield. Complex 2 was characterized by IR,1H NMR , and single crystalx-ray diffraction analyses. The cluster can be viewed as a dodecahedron of eight metal atoms capped with two ruthenium carbonyl groups, two triply bridging EtC2Et ligands and one quadruply bridging EtC2Et ligand. Application of the standard electron counting procedures indicate that this is an unusual complex in which the 18 electron rule applies and the polyhedral skeletal electron pair theory does not. Crystal Data for 2 2.0.5 CH2CI2: space group = P21,a = 12.759(2) A,b=18.438(2)Å,c = 20.197(3) Å,β = 91.59(1)°, Z. = 4, 6394 reflections,R = 0.037.
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  • 10
    ISSN: 1572-8927
    Keywords: Solvolysis ; kinetics ; aqueous solvent mixtures ; Co(III) complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the solvolysis of [Co(CN)5Cl]3− have been investigated in water +2-methoxyethanol and water + diethylene glycol mixtures. Although the addition of these linear hydrophilic cosolvent molecules to water produces curvature in the variation of log(rate constant) with the reciprocal of the dielectric constant, their effect on the enthalpy and entropy of activation is minimal, unlike the effect of hydrophobic cosolvents. The application of a Gibbs energy cycle to the solvolysis in water and in the mixtures using either solvent-sorting or TATB values for the Gibbs energy of transfer of the chloride ion between water and the mixture shows that the relative stability of the emergent solvated Co(III) ion in the transition state compared to that of Co(CN)5Cl3− in the initial state increases with increasing content of cosolvent in the mixture. By comparing the effects of other cosolvents on the solvolysis, this differential increase in the relative stabilities of the two species increases with the degree of hydrophobicity of the cosolvent.
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